The subject matter disclosed herein generally relates to digital motor controls, and more particularly to a resolver-to-digital converter using a delta-sigma modulator.
A resolver can be used in a feedback control loop of a motor, such as a direct current (DC) motor. Resolvers are position sensors used in high performance motor drives for precise closed-loop control. Once accurate position is determined, known motor control algorithms can be used to adjust operation of the motor. To determine position, a decoding algorithm is used to convert analog signals generated by a resolver to a digital word representing the true position of the motor shaft. The decoding is typically performed by an expensive resolver-to-digital converter (RDC) chip. As an alternative to using the RDC chip, other conversion systems have been proposed. At low motor shaft speeds contemporary decoding algorithms may provide adequate performance. However, as operational speed of the motor increases, the effective resolution of the motor position decreases when using contemporary decoding algorithms. Insufficient effective resolution of the motor position typically results in a loss of motor control accuracy.